Of course, drone flybys are nothing new: the small, hovering, camera-equipped unmanned aircraft have been making sketchy appearances all around the world's major landmarks this year. Just last week, a guy landed a drone carrying radioactive sand onto Japanese Prime Minister Shinzo Abe's office roof. Earlier this year, another drone (sans contaminated granules) crashed near the White House, and others were seen around the Eiffel Tower.

With bridges in particular, drones can gain easy aerial access to the otherwise inaccessible structures. This can be good and bad: Some civil engineers think that we can use drones to survey the structural condition of the beams and joints of a bridge — which can be especially advantageous with older structures. (The Golden Gate Bridge was built around 80 years ago.)

But law enforcement is on the lookout for people who might use the information-gathering technology for nefarious purposes. Last year, two men were arrested after they were caught flying drones near New York City's George Washington Bridge, nearly coming within striking distance of an NYPD helicopter at 600m. Right now, laws surrounding personal and recreational drone use are still pretty nebulous.

As far as the Golden Gate Bridge goes, though, they take security pretty seriously. Since 9/11, the Golden Gate Bridge Highway and Transportation District received around $US15 million in grants to beef up security. Sounds like some of that could be going toward anti-drone enforcement.

Using ground-penetrating radar, scientists detected a massive reservoir of frozen water sandwiched by layers of sand beneath the northern polar ice cap on Mars. This reservoir contains so much ice that, if melted and brought to the surface, it would submerge the entire planet.